"Whatever happens on Thursday, it will be a victory for the Coalition that the Conservatives lead, and a defeat for Miliband; and if Maria Hutchings pulls it off – the first Conservative by-election victory, in government, for more than 30 years – it will be stupendous."

And stupendous it would be, if it were actually true.

You see the Conservative party have won not one, but EIGHT by-elections while in government over the past thirty years.

What they haven't done in over thirty years is gain a seat at a by-election, while in government. The last time they did that was in 1982.

"I cannot believe Miliband will pursue this policy through to the election. If he does, he will have signed his political death warrant."

His political death warrant? This mansion tax must threaten a lot of voters then?

Well no. According to the ONS, just 1.2% of all properties are priced over £1 million in the UK and they don't even bother to give a figure for properties over £2 million.

I wonder how much Boris's home is worth?

Well according to the Land Registry, Boris bought his Islington home four years ago for £2.3 million:

Since then it has risen in value to over £2.6 million, according to one estimate:

A £326,000 increase in just four years. Trebles all round!

So what's Boris so worried about?

"The end result [of a mansion tax] would be in many cases to force sales, and to reduce the value of property – and for a country whose wealth is, for better or worse, so tightly tied to property, that would not be a good outcome."

Well it certainly wouldn't be a good outcome for Boris and his £2.6 million home. What about the rest of us?

"Yes, of course we need people to be able to afford to live in Britain. But the answer is not to make it even more punishing to own a home in an expensive part of the country. The answer is to get going with a massive programme of house-building on the many brownfield sites."

Ah housebuilding. We're finally on to something to do with Boris's day job.

"If you listen to Nick Boles, the housing minister, you can see that he understands the urgency of the problem."